Apparatus for preventing collision of vehicles

ABSTRACT

An apparatus for preventing collision of a vehicle comprises 
     A device for measuring a distance R from a driving vehicle to an obstacle and a relative velocity V of the driving vehicle to said obstacle; 
     A circuit for generating a damping signal when the relation of the distance R, the relative velocity V and a preset deceleration α becomes the relation of R &lt; V 2  /2α; 
     a deceleration detector for detecting the actual deceleration α&#39; of the driving vehicle; 
     A correction circuit which compares the actual deceleration α&#39; detected by the deceleration detector with the preset deceleration α and the damping signal is corrected depending upon the comparative data.

BACKGROUND OF THE INVENTION

The present invention relates to an apparatus for preventing collisionof a vehicle which imparts a damping of a driving vehicle according to apreset deceleration without being affected by a condition of contactbetween a surface of road or railway and wheels of the vehicle.

Heretofore, it has been known to provide an apparatus for preventingcollision of a vehicle by damping the vehicle by measuring a distance Rfrom the driving vehicle to an obstacle such as a forward vehicle or astopping vehicle and a relative velocity V thereof and damping thedriving vehicle by generating a damping signal when the relation of

    R-R.sub.0 < (V.sup.2 /2α)

wherein R₀ represents the nearest distance and α represents a presetdeceleration, is given.

The damping apparatus has been employed for preventing the collision ofvehicles. Referring to FIG. 1, the known damping apparatus will beillustrated in detail.

In FIG. 1, the distance R from the vehicle to the obstacle is plotted onthe abscissa and the relative velocity V is plotted on the ordinate.

The driving vehicle approaching to the obstacle at a relative velocityof V = V₁ = constant can be shown as the line 11. When the curve 12 isshown by R-R₀ = V² /2α, the curve 12 crosses the line 11 at the distanceof R₁ - R₀ = V₁ ² /2α. The cross point is given as A. The drivingvehicle approaching at a constant velocity V₁ is controlled with aconstant damping by the damping signal for the preset deceleration α atthe cross point A.

Thus, if the actual deceleration α' of the vehicle has resulted becauseof the effect of friction between the wheels (tires) and a surface ofroad, the vehicle gradually approaches the shortest distance R₀ to theobstacle along the deceleration curve 12 in the case of α = α', wherebythe relative velocity of the driving vehicle becomes zero in theshortest distance R₀ and the driving vehicle avoids collision with theobstacle.

Thus, even though the damping is generated by the preset deceleration α,it is rare that α precisely equals α' because of the effect of frictionbetween the surface of road and the wheels.

One way to overcome this problem is to determine the deceleration αafter considering the effect of the friction between the surface of theroad and the wheels. However, the effect of friction are not easilydetermined because of the number of variables involved.

In the case of α' > α, excess damping is applied and the curve 13 fromthe point A in FIG. 1, and the relation of R - R₀ > V² /2α is given at acertain point on the curve 13 to release the damping signal whereby thedriving vehicle drives at a constant velocity toward the point C on thecurve 12.

Thus, the damping is also applied at the point C and the excess dampingphenomenon is repeated at the points D and E. The intermittent dampingsare applied and a smooth damping can not be attained.

The intermittent damping is applied because of the delay of themechanical system of the damping apparatus from the time of thegeneration of the damping signal to the actual performance of thedamping operation.

In the case of α' < α, the driving vehicle has the velocity V₂ even inthe nearest distance R₀ as shown by the curve 14 in FIG. 1. Therefore,when α' < α there is a possibility of a rear-end collision with theforward obstacle (vehicle, etc.) which is quite a dangerous condition.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide an apparatus whichprevents collision of a vehicle without intermittent damping operation.

Another object of the present invention is to provide an apparatus whichprevents collision of a vehicle by controlling the velocity of thevehicle without being affected by frictional effects between the wheelsand the surface of road.

The foregoing and other objects of the present invention have beenattained by providing an apparatus for preventing collision of a vehiclewhich comprises a device for measuring a distance R from a drivingvehicle to an obstacle and a relative velocity V of said driving vehicleto said obstacle; a circuit for generating a damping signal when therelation of the distance R, the relative velocity V and a presetdeceleration α becomes the relation of R < V² /2α; a decelerationdetector for detecting the actual deceleration α' of the drivingvehicle; a correction circuit which compares the actual deceleration α'detected by the deceleration detector with the preset deceleration α andgenerates a corrected damping signal in accordance with the comparativedata.

BRIEF DESCRIPTION OF THE DRAWINGS

Various objects, features and attendant advantages of the presentinvention will be more fully appreciated as the same becomes betterunderstood from the following detailed description of the presentinvention when considered in connection with the accompanying drawingsin which:

FIG. 1 is a graph of characteristic curves showing the principles of theconventional apparatus and the apparatus of the present invention;

FIG. 2 is a block diagram of the apparatus of the present invention.

FIG. 3 is a view of an acceleration α presetting device.

FIG. 4 is a block diagram of the deceleration detector 4 shown in FIG.1.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

A preferred embodiment of the novel apparatus for vehicle collisionprevention according to the present invention will be described indetail by referring to FIG. 2.

The principle of the present invention will be also described byreferring to FIG. 1 in the description of the embodiment of FIG. 2.

In FIG. 2, the reference numeral 1 designates a radar for measuring thedistance R from the driving vehicle to the obstacle and the relativevelocity V; 2 designates a decision circuit for determining whether thedistance R is more or less than the value of V² /2α and for generating adamping signal S(α) corresponding to the deceleration α when thedangerous condition determined by the relationships of the presetdeceleration α, the distance R and the velocity V exists.

The reference numeral 3 disignates a preset circuit for the presetdeceleration α; 4 designates a deceleration detector for detecting theactual deceleration α' or a circuit for calculating the deceleration asthe differential of the velocity of the driving vehicle; 5 designates acomparing circuit for detecting a difference Δ α = α - α' wherein αdesignates the preset deceleration and α' designates the actualdeceleration 6 designates an amplifier for amplifying the difference Δα; 7 designates a correction circuit for correcting the output of thedecision circuit 2 in response to the output signal of the amplifier 6;and 8 designates an output terminal for the damping signal.

The operation of the embodiment of the apparatus of the presentinvention will be described by referring to FIG. 1 showing the principleof the invention.

As discussed above for the conventional apparatus, the driving vehicleis approaching an obstacle at a constant relative velocity V₁ as itmoves from right to left on the line 11 of FIG. 1.

When the driving vehicle approaches the obstacle at the distance R₁ thatis the point A of FIG. 1, the decision circuit 2 generates the dampingsignal S(α) corresponding to the deceleration α as that of theconventional apparatus.

In the correction circuit 7, the damping signal S(α') = S(α) generatedis fed to the damping system from output terminal 8 without anacceleration correction factor until the deceleration α' is actuallygiven to the driving vehicle.

Accordingly, in the initial condition of the damping operation, thedamping is applied by the damping signal S(α) given depending upon thepreset deceleration α (the damping signal being the same as that of theconventional apparatus).

Then the apparatus of the invention umplements a damping techniquedifferents than that of the conventional apparatus.

When damping is actually applied by the damping signal S(α), thedeceleration detector 4 detects the actual deceleration α' of thedriving vehicle. When the actual deceleration α' is detected by thedeceleration detector 4, the difference Δ α = α - α' between α' and thepreset deceleration α is immediately detected by the comparing circuit5. The comparing circuit 5 generates the signal Δ α = 0. The actualdeceleration α' is not detected by the deceleration detector 4 duringthe time the damping signal S(α) corresponding to the presetdeceleration α is generated by the decision circuit 2 until a constanttime given by the response speed of the mechanical system.

The difference Δ α given by the comparing circuit 5 is amplified by theamplifier 6 and is fed to the correction circuit 7. Correction Circuits7 converts the damping signal S(α) into the corrected damping signalS(α'), and thereby imparts the actual deceleration.

Referring to FIG. 1, in the case of α' > α, the driving vehicle has thevelocity along the curve 13 from the point A, however, it changes alongthe curve 15 when the actual deceleration α' is detected by thedeceleration detector 4 and it gradually reaches to the curve 12.

In the case of α' < α, the driving vehicle has the velocity along thecurve 14 from the point A, however, it changes along the curve 16 andgradually reaches to the curve 12.

It is possible for the driving vehicle to reach the predetermineddeceleration curve within a time shorter than that of the conventionalapparatus, by use of the above-mentioned damping correction.Accordingly, it is possible to attain the smooth damping having shortdamping time without intermittent damping as in the conventionalapparatus.

The result of the invention can be understood by the principle shown inFIG. 1 and the embodiment of FIG. 2.

The preset circuit 3 for the preset deceleration α will be furtherillustrated referring to FIG. 3.

When the deceleration α is digitally preset, a digital switch shown inFIG. 3 can be used.

The output of the digital switch can be as follows.

Binary Coded Decimal L11-02A; L10-02A; L20-02A; T11-02A; T10-02A;T20-02A.

    ______________________________________                                                        Terminal of COM is connected to output                        Dial            terminals shown as •                                    Position                                                                             Symbol   1        2      4      8                                      ______________________________________                                        0      0                                                                      1      1        •                                                       2      2                 •                                              3      3        •  •                                              4      4                        •                                       5      5        •         •                                       6      6                 •                                                                              •                                       7      7        •  •                                                                              •                                       8      8                               •                                9      9        •                •                                ______________________________________                                    

The deceleration detector 4 for detecting the actual deceleration α'will be further illustrated referring to FIG. 4.

The deceleration detector 4 includes a strain tester having a straingauge at one line of a wheatstone bridge and an A-D converter forconverting the output of the tester to digital signal.

One embodiment of the circuit of the decelerator detector 4 is shown inFIG. 4.

In FIG. 4, the reference numeral 11 designates a gauge bridge; 12designates an inner bridge; 13 designates a carrier wave amplifyingcircuit; 14 designates a phase detecting filter circuit; 15 designates aDC amplifying circuit; 16 designates an A-D converter; 17 designates abridge voltage amplifying circuit; 18 designates an oscillating circuit;19 designate ±12V stabilizing power source circuit; and 20 designates aconverter circuit.

In the gauge 11 bridge, A gage designates an active gage and D gatedesignates a dummy gauge (temperature compensation) which is keptequivalent to the A gauge so as to prevent strain.

The AC voltage of the amplified oscillation circuit 18 is applied to thebridges 11 and 12. The equilibration of the resistance and thecapacitance of the bridges 11 and 12; is held by a varistors VR102 andVR103.

When the strain is given to the A gauge, the AC voltage of theoscillation circuit 18 modulated depending upon the strain and is outputfrom the bridge 11. The output voltage is amplified in a carrier waveamplifying circuit 13 and the positive or negative modulation of thestrain is discriminated by the phase detecting circuit 14, and thesignal is also filtered in phase detecting filter circuit 14 to convertthe waveform to a corresponding electric signal. The electric signal isamplified by DC amplification circuit 15 and the signal is measured byan oscillograph or the other recorder.

The output waveform of the bridge is converted to the digital signal bythe A-D converter 16 so as to detect the actual deceleration α'.

As described above, in accordance with the invention, the collision ofthe vehicle can be prevented by the smooth damping without beingaffected by the conditions of the surface of road and railway, thecondition of wheels and the condition of friction and contact of thewheels to the surface of road depending upon the weather.

Moreover, the complicated effects in the above-mentioned condition canbe transitionally overcome by the automatic correction depending uponthe variation of the conditions of the surface of road, wheels, etc.,and the response of the mechanical system.

What is claimed is:
 1. An apparatus for preventing collision of avehicle comprising:a device for measuring a distance R from a drivingvehicle to an obstacle and a relative velocity V of said driving vehicleto said obstacle; a circuit for generating a damping signal when therelation of said distance R, said relative velocity V and a presetdeceleration α becomes the relation of R < V² /2α; a decelerationdetector for detecting the actual deceleration α' of said drivingvehicle, said deceleration detector including oscillator circuit meansfor generating an unmodulated carrier wave, strain gauge bridge meansconnected to said oscillator circuit means for modulating said carrierwave in accordance with said actual deceleration α', and demodulatingcircuit means connected to said strain gauge bridge means fordemodulating said modulated carrier wave and generating a signalproportional to said actual deceleration α'; and a correction circuitfor comparing the actual deceleration α' detected by said decelerationdetector with the present deceleration α and correcting the dampingsignal depending upon the comparative data.
 2. An apparatus forpreventing collision of a vehicle according to claim 1, wherein saiddevice for measuring the distance and the relative velocity is a radardevice.
 3. An apparatus for preventing collision of a vehicle accordingto claim 1, wherein said deceleration detector comprises a circuit forcalculating said actual deceleration α' from a velocity signal of saiddriving vehicle.
 4. An apparatus for preventing collision of a vehicleaccording to claim 1 wherein the actual deceleration α' is calculated bytaking the differential of a velocity signal of said driving vehicle. 5.An apparatus for preventing collision of a vehicle according to claim 3wherein the actual deceleration α' is calculated by taking thedifferential of a velocity signal of said driving vehicle.